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The outbreak is blamed for 10 deaths; there have been 100 reported cases

An investigation is still trying to determine the source

New York (CNN)The number of those affected by the Legionnaires' disease outbreak in New York City rose yet again Thursday -- with 10 deaths among the 100 total cases.

Two more deaths were reported Thursday, up from eight the previous day and seven on Tuesday. All the deaths originate in the same area in the South Bronx, Mayor Bill de Blasio, who'd earlier indicated those afflicted were older adults with additional underlying medical problems.

All but a handful of those who have come down with Legionnaires' have been hospitalized, while roughly half have since been treated and released.

Five cooling towers have tested positive for Legionnaires' disease, and decontamination has commenced, including on the cooling tower on the top of Lincoln Hospital, de Blasio said earlier this week. The city believes it has identified all of the targets that have been contaminated.

Legionnaires' disease is a respiratory bacterial infection usually spread through mist that comes from a water source, such as cooling towers, air conditioning or showers. It is not transmitted person to person. Symptoms of the disease include fever, chills and a cough.

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Most people recover, but between 5% to 30% of those who get the disease die, according to the U.S. Centers for Disease Control and Prevention. An estimated 8,000 to 18,000 hospitalized cases of Legionaires' disease occurs each year in the United States. An outbreak of the disease in Philadelphia in 1976, largely among people attending a convention of the American Legion, led to its name.

"We are conducting a swift investigation to determine the source of the outbreak and prevent future cases. I urge anyone with symptoms to seek medical attention right away," Dr. Mary Bassett, commissioner of New York City's health department, said last month.

The department's probe includes testing water from potential sources in the area.

De Blasio reiterated there is no risk to the city's water supply.

Bronx Borough President Ruben Diaz Jr. said on Friday that his office will push for legislation to create a citywide inspection system that would test building water infrastructure for the disease and others.